Catalytic cracking of hydrocarbons



Nov. 23, 1948. J. A. R|DGwAY, JR... Erm. 2,454,515

cATALY'rIc cnAcxIsa or mnocmons 2 Suda-Shut 1 Filed Nov. 12, 1943 gusJal,

VPatented Nov. 23, 1948 UNITED STATES PATENT OFFICE CATALYTIC CRACKING FHYDROCABBONS John A. Ridgway, Jr., Texas City, Tex., and Philip Hill,Hammond, Ind., assignors to Pan American Refining Corporation, New York,N. Y., a corporation oi Delaware Application November 12, 1943, SerialNo. 509,974

12 Claims.

l This invention relates to the cracking of hydrocarbon oils and moreparticularly it relates to the use of liquid hydroiluoric acid as acatalyst in cracking heavy oil and heavy naphtha. Still y moreparticularly the invention relates to the crackin-g of petroleum gas oilinto gasoline, gas and asphalt in the presence of liquid hydrofluoricacid. One object of the invention is to convert heavy hydrocarbons andparticularly gas oil into gasoline, gas and asphalt in the presence of acatalyst, substantially without the formation of carbon or carbonaceouscompounds of such a character as to absorb or destroy the catalyst.

Another object of the invention is to provide a4 We have now found thatwhen substantially process for cracking heavy hydrocarbon oils anhydrousliquid hydrofluoric acid is employed which will produce a minimum amountof dry gas as a cracking catalyst in substantial amounts. and a maximumamount of condensable hydrothe conversion may be carried out withsubcarbon gases of isoparainic structure. Still stantially no carbonformation but with the another object of the invention is to provide aformation of a great deal of asphalt, tar. or heavy hydrocarbon crackingprocess which selectively converts a major part of the oil to gasolineand asphalt or heavy fuel oil of high heating value with a minorproduction of xed gases. Other objects of the invention will becomeapparent from the description which follows.

The invention is illustrated by a drawing which shows diagrammaticallyin Figure 1 an apparatus for carrying out the process. Figure 2 is agraph of data obtained in the process.

Heretofore the catalytic cracking of heavy oils has been beset by thegreat diillculty of catalyst deterioration, some processes requiringhigh catalyst replacement and others requiring frequent catalystregeneration at considerable expense. In the case of a catalyst such asaluminum chloride employed in the well-known McAfee process, thealuminum chloride suffered rapid contamination resulting in extensivealumi- In the case of high temperature catalytic fuel, i. e. highboiling conversion products. On distillation of the conversion residue,we have found V'that the hydrouoric acid catalyst, having formed acidcracking were employed with the following characteristics:

num chloride losses owing to catalyst degenvir Recycle eration. Thecause of degeneration is generally 40 G o G o traceable to theinteraction of the heavy hydros me Gram o 83 o al carbons and theirbreakdown products with the Afine pom 'fljjjjjjjjjjj: "I: '170 'maluminum chloride. forming more or less stable Distliltv-ASTMJ F 454 462addition products or a sludge of no catalytic value. 307:: 482 m5 Manyattempts have been made to regenerate the aluminum chloride but withoutmuch com- 907; f 575 w8' mercial success volumetric Averge BoilingPOlit, F 513 53A The reaction was carried out in a bomb under theconditions set forth as follows:

Run #l Run #2 Run #3 Vir in Gai Oil Recycle WLM 5'.. U. #1 ons Per centCat. by Wt 295 193 191 Per cent Cat. by V01. 234 158 158 Per cexlit Cat.by Mols 3. 202 2, 160 2, 28g iergmf III 155-155 155-162 155-161 Max.pressure, iba/sq. in 91 about 850 Product- Wt. Per Cent of Charge 0.220. 08 0. -19 0. 46 4. 05 2. 47 3. 39 2). 3 14. 20 10. 88 2.13 1.11 l. 237. 27 20 5. l0 l. 16 0. 60 1.52 35.1 24. 6 23. l

6. 3. 9 -s-a s; -9 200+ Total Gasolio l0. 7 12. o Totll ecycle Stock.5:2 nl sia Yield Date (Bueil on amount reacting):

Totalgas (Ci, C4, 'Ca and lighter), per

38. (i 31. 0 Goline (Ct-m0" C per cent 11.7 15.9 Gas-i-gasoline, percent o0. 3 4o. 9 Tar,percent 49.7 53.1

These data show that the proportion of catalyst employed in theconversion is of considerable importance in determining the extent ofconversion obtained. Thus the total amount of conversion (totalreacting) in run 1 with 295% of HF was 91 compared with onLv 79.3 in run2 in which all the conditions were the same except the proportion ofcatalyst was 193% by weight instead of 295. In general, it is desirableto employ an amount of catalyst equal to at least half the Reid vaporpressure.

weight of the oil treated, and a catalyst-oil ratio increased proportionof catalyst to oil. (Note yield based on percent reacting 49.7 v. 53.1.)The temperature employed with liquid HF cracking catalyst is unusuallylow for catalytic conversion reactions, the range in temperature usuallybeing about 100 to 230'C. and preferably about 140 to 175 C.

The reaction time may be varied over a considerable range dependingprimarily on the temperature and the ratio of catalyst-to-oil treated.Thus in an example in which 193% of HF was used to convert 4virgin gasoil, the total gas yield obtained from virgin gas oil at 135 to 145 C.was only 2.4% yat a reaction time of 2 hours and '7% at 5 hours reactiontime. However, in another example with the same catalyst concentrationbut with a conversion temperature of 155 to 160 C. an increase inreaction time of from 1% to 4 hours increased the gas yield from 2.4 to24.6 percent. In general it appears that a conversion temperature of 150C. or above is necessary for appreciable gas production within a periodof four hours or less.

The apparent low yield of "gaso1ine must be corrected by adding theretothe C5 and most of the C4 hydrocarbons when comparing with the usualconversion data on gasoline of 9 to 12 pounds On this basis the gasolineyield in run 2 would be about 44% based on amount reacting..

Referring to Figure 1 of the drawing, a suitable feed stock, for examplea virgin gas oil of A. P. I. gravity having a boiling range of about 345to 650 F. is charged to the system by line I0 leading to mixer Il. Anysuitable mixing device may be used such as an orifice mixer consistingof a series of orice plates thru which the feed stock is forced to flowat high velocity. Liquid HF is charged to the system by line I2 andmixed with the hydrocarbon feed in mixer Il. The mixture then fiows byline i3 to reaction chamber I4. The volume of the reaction chamber issumcient to provide the desired reaction time, for example ten minutesto four hours depending on the temperature, character of the feed stock,etc. For short reaction times, a coil reactor may be used. The amount ofHF employed in the reaction is suillcient to maintain a separate liquidcatalyst phase and it is desirable to employ a considerable excess abovethat required to saturate the hydrocarbons.

'I'he temperature of the reaction zone I4 is maintained above 100 C. andgenerally within the range of 125 to 200 C.. a suitable temperaturebeing about 150 to 160 C. Higher temperatures may be employed for shortreaction periods. Any suitable heating means may be employed for thepurpose, for example coil 14a supplied with heated oil, steam or otherheating fluid. We can also preheat the HF and feed in separate heaters,not shown, previous to mixing in mixer Il.

The mixture of hydrocarbon stock and El" in reactor Il is maintained ina highly agitated condition in order to obtain the necessaryl contactbetween the two liquid phases to effect catalytic conversion. Mechanicalagitators may be installed directly in the reaction chamber or theagitation may -be provided both internally and externally of thereaction chamber as shown in the drawing. According to this method thereaction mixture is withdrawn by line I5 from the bottom of chamber I4and conducted by centrifugal pump I6 thru line I'I back to the top ofthe reaction chamber. By maintaining a high recycle ratio, any desireddegree of interspersion of the liquid catalyst phase and the oil phasemay be obtained. 1

A controlled stream of reaction products is withdrawn by valved line Illeading thru cooler I8a to gas separator I9 from which some of thelighter gaseous reaction products can be withdrawn by line 20. Liquidreaction products are conducted byline 2| to catalyst settler andseparator 22. Bettler- 22 is preferably a horizontal, cylindrical,elongated chamber thru which the reaction products flow continuouslywithout agitation, thereby allowing the heavy liquid HF and associatedasphalt to separate at the bottom of the settler 22. This catalyst layercontaining some heavy hydrocarbons in solution can be conducted directlyby line 2l back to the feed mixer I I wherein it is mixed with freshamounts of hydrocarbon feed stock and returned to the reactor Il. 0r e.part or all of the stream may be diverted thru asphalt separator 24wherein H1' is distilled from the asphalt, the HF being condensed -lncondenser 25 and recycled by line 2l while asphalt is withdrawn by line21.

I'he hydrocarbon reaction products are withdrawn from settler 22 by line2l and valve 28, thence to neutralizer 38 wherein traces of HF dissolvedin the hydrocarbon stream are remr'ed by an alkaline neutralizing agentsuch as sodium carbonate, sodium hydroxide, lime, etc., either solid orin solution, or by adsorption with a suitable adsor-bent for HF such asi'ullers earth, silica gel, bauxite, or one of the acid-absorbingnitrogenbase resins employed in water treating. In the case of certainstocks and types of operation where the amount of HF dissolved in theproducts withdrawn from the upper part of settler 22 is appreciable, wemay recover the HF, for example, by stripping in place of neutralizing.In this case neutralizer 30 may be substituted or preceded by astripping column and the recovered HF vapor may be recycled to the mixerI l.

From neutralizer 30 reaction. products pass by line 3l to fractionator32. Heat is supplied to the fractionator by reboiler coil 33 and reiluxby cooling coil 34. Light products including butanes and lighterhydrocarbons are distilled off thru line 35 leading to fractionator 48.

The principal liquid hydrocarbon products are withdrawn from the bottomof fractionator 32 by line 38 and heated in heater 3l, which may be apipe still for example. From heater 31 the liquid products are conductedby line 38 to fractionator 39 provided with gas oil and gasoline sidestrippers 40 and 4| respectively. A heavy fraction suitable for fuel oilor asphalt manufacture is withdrawn at the bottom by line 42. Heatrequired for reb'oiling in fractionator 38 is supplied by coil 43 whilereflux cooling is supplied by coil44. The gas oil fraction withdrawn byline 45; if desired, may be conducted back to mixer il as feed stock forthe process. The gasoline withdrawn by line 46 is essentially a heavyblending naphtha.

Pentane and lighter hydrocarbons are withdrawn from fractionator 33 byvapor line 41 leading to fractionator 48 to which vapors fromfractionator 32 may also be conducted. Propane and lighter products aredischarged by vapor line 49 while pentane is removed as the bottom stockby line 50 and butane is withdrawn by line 5i from side stripper 52. Thepentane and butane streams produced in the process consist largely ofisopentanel and isobutane. The isopentane is chiefly valuable forblending in aviation fuels and other high knock rating gasoline. Bothisopentane and isobutane may be subjected to alkylation with suitableoleilns, for example ethylene, propylene or butylene, to producealkylate gasoline, neohexane, isooctane, triptane, etc., very desirablel constituents of aviation fuels.

In the cracking of virgin gas oil, gas production. has been found todecrease with increasing reaction pressure. When the reaction pressureis increased from 1290 to 2100 pounds per square inch gauge, a sharpdecrease in total gas yield and tar formation are noted with increasedproduction of recycle stock, while the gasoline yield remainsessentially constant. Data on the yields of gas, gasoline and tarcompared with percent of stock cracked show that the rate of tarproduction increases regularly with the extent of cracking While thegasoline reaches a maximum with conditions producing a total conversionof labout'65 percent. In Figure 2 are plotted data showing anaccelerated production of the isoparaiiln gases with isobutane exceedinggasoline production at about 19 percent.

As indicated hereinabove one of the important advantages of this processof hydrocarbon conversion over other catalytic processes lies in thesubstantially complete recovery of catalyst without necessity ofregeneration. Most of the catalyst separates as a separate liquid layerwhile the remainder is removed by simply stripping or distilling thecatalyst from the reaction products. Substantially no undecomposablesludge or catalyst is formed in the reaction and therefore very littlefresh catalyst need be added by way-of replacement beyond that necessaryto compensate for mechanical losses.

Hydrogen may also be employed in the HE conversion reaction to modifythe character and amount of tar or asphalt formed. The amount employedcan be in the range of 1000 to 3000 cubic feet per barre'l of oiltreated. Hydrogen pressures of 500 to 3000 pounds per square inch aresuitable. Hydrocarbon gases containing hydrogen may be used instead ofhydrogen and hydrogen-containing gases produced in the process may thusbe employed. In the HF catalytic cracking process the gas producedconsists chiefly of butanes and pentanes and in most cases thesefractions contain about 88 to 93 of isoparamns. No neopentane has beendetected. The butane yields are especially high; for example 22.4% fromvirgin gas oil and 28.7% from dodecene was obtained. The heaviercharging stocks tends to produce less dry gas, that is, :propane andlighter hydrocarbons and hydrogen, than the lighter charging stocks. Allgas is completely saturated. If desired, the C4 and C5 fractions may beallowed to remain with the gasoline instead of being separatedas shownhereinabove. It is generally preferred to operate the process withsuillcient cracking to yield products having a 90% point- ASTM-below the10% point of the charging stock.

The concentration of isobutane and isopentane is much higher than wouldbe expected from the equilibrium vaues calculated from thermodynamicdata, which may indicate that isomerization occurs prior to orsimultaneously with the cracking reaction in the presence of HF. Forcomparison, the concentration of isobutane in the ggilytic isomerizationof butane is only .about l The ,gasoline obtained in the process issubstantially free of unsaturationand a cut from hexane to 200 C. had aknock rating of 57 by the ASTM method which was determined in a 20%blend with reference fuel. Inclusion of isobutane and isopentaneproduced in the process would of course increase the knock rating veryconsiderably, and it is estimated that a gasoline fraction containingsufficient ofthe lighter hydrocarbons to give a vapor pressure of 10pounds R. V. P. will have a knock rating of 67.5, ASTM. However, becauseof the high concentration of isopentane (about 90%) in the Cs fraction,it is usually more desirable to use this stock in aviation'fuel blendingwhere isopentane commands a high premium.

The tar produced in the process is characterized by high specificgravity, for example about 1. It can'be employed as a heavy fuel orconverted into asphalt by heating and/or blowing with air.

Although we have described our process as it is applied to theconversion of gas oil, it may also heavier than gasoline to form gas andgasoline components including low boiling yisoparafiinic hydrocarbonswhile simultaneously forming tar, which comprises subjecting said oilsto the action of a catalyst consisting of hydroiluoric acid in an amountat least equal to the weight oi oil treated, maintaining the temperatureof the reaction zone within the range of about 100 to 250 C.,maintaining suihcient pressure in the reaction .zone to keep thecatalyst in liquid phase, malntaining the hydrouoric acid in intimatecontact with said oils in said reaction zone for a time of contactsufllcient to eil'ect cracking as the predominant reaction, removing thehydrocarbon products from the reaction zone, removing dissolved catalysttherefrom by 4distillation and returning it to the reaction zone andrecovering isobutane, isopentane and other hydrocarbons of the gasolineboiling range from the hydrocarbon products. n

2. The process of claim 1 wherein a gas oil fraction is separated fromthe products and recycled to the reaction zone for further cracking.

3. The process of cracking heavy hydrocarbon oil boiling above thegasoline boiling range to produce isoparafflnic hydrocarbons, whichcomprises contacting said oil with at least `50% by weight of a catalystconsisting on anhydrous liquid hydrofiuoric acid at a temperature in therange of about 100 to 250 C., introducing hydrogen into the reactionzone in an amount of about 1000 to'3000 cubic feet per barrel of heavyoil treated, maintaining suillcient pressure on said reaction zone tokeep the catalyst in the liquid phase, continuing the reaction untilsaid heavy hydrocarbon oil is substantially converted into hydrocarbonsboiling in the gasoline boiling range, yrecovering catalyst from thereaction products and returning it to said reaction zone, and separatingfrom the reaction products tar, gasoline boiling range hydrocarbons andhydrocarbon gas.

4. A process for the production of isoparaiiinic hydrocarbons whichcomprises contacting a normally liquid petroleum hydrocarbon chargingstock oil with acatalyst consisting of hydrogen fluoride in a reactionzone, said hydrogen fluoride being present in said reaction zone in suchquantities under reaction conditions as to give a twoliquid phasesystem, maintaining intim-ate contact between the two liquids in saidliquid phases at about 100 to 230 C. for a period of time sunlcient togive cracking as the predominant reaction whereby lower boilingproducts4 including isoparafilns are produced, and recovering bydistillation an isoparaiiin-rich hydrocarbon product having a 90% pointin the ASTM distillation below the point of the said hydrocarboncharging stock.

5. A process for the production of isoparainic hydrocarbons whichcomprises contacting a hy-v drocarbon oil fraction in a reaction zonewith at least 50% by weight of a catalyst consisting of hydrogen uoridein said reaction zone and under suillcient pressure to produce twoliquid phases. under reaction conditions, agitating said liquidl phasesat about 100 to 300 C., separating said catalyst from the reactionproducts, recovering from said reaction products a product comprisingisoparafiinic hydrocarbons, said product having a boiling rangesubstantially below that of said charging stock and returning asubstantial portion of said catalyst to said reaction zone.

6. The process of claim 4 wherein the tempera- `140 to 200 C. -r 7. Theprocess ot cracking heavy hydrocarbon.

ture of the reaction lies within oils into lower boiling isoparamnichydro'arbons, which comprises subjecting said oils at a temperature ofabout to 250 C. to the action ot at least 50% by weight oi' a catalystconsisting of liquid hydrouoric acid, injecting suillclent hydrogen intothe reaction mixture to maintain the pressure in the range of about 500to 3000 pounds per square inch, maintaining intimate contact between theliquid hydrofluoric acid and the oil, by agitating the reaction mixturefor a periodi of time until said oil has been substantially converted tolower boiling isoparafilnic hydrocarbon products, separating said lowerboiling products from hydrogen and hydrouoric acid and recycling saidhydrogen and hydrofluoric acid to said contacting step.

8. The process-of cracking gas oil which comprises subjecting said oilin a reaction zone to the action of a catalyst consisting of liquidhydropredominant reaction, withdrawing the reaction products from saidreaction zone and recovering gasoline boiling range hydrocarbons, gasand tar therefrom.

9. The process of cracking heavy hydrocarbon oils which comprisessubjecting them at elevated temperature to the action of at least 50% byweight of a catalyst consisting of liquid HF under superatmosphericpressure, maintaining suicient pressure to keep the HE' in liquid phase,employing a temperature above 100 C. and time of treating to eiectcracking of said heavy oils to lighter hydrocarbon products as thepredominant reaction, separating the HF from the reaction products bysettling, recycling the separated HF to the cracking operation andseparating from the hydrocarbon products gas, gasoline boiling rangehydrocarbons and at least one heavier fraction comprising tar.

10. 'IIhe process of cracking a heavy hydrocarbon oil boiling above thegasoline boiling range which comprises contacting said oil with at least50 per cent by weight of a catalyst consisting of hydroiuoric acidcatalyst at a temperature in the range of about to 200 C., maintainingsuillcient pressure in the reaction zone to keep the catalystsubstantially in liquid phase, maintaining said oil and catalyst inintimate contact with each other for a time of contact sufficient toeffect cracking as the predominant reaction, separating said catalystfrom reaction products, recovering from said reaction products a productcomprising isoparaninic hydrocarbons, said prodthe range ot aboutl about125 to 200 C. under a. pressure'sufcient to effect cracking aslthepredominant reaction whereby a substantial portion ofv said oil isconverted into low-boiling isoparafln hydrocarbons and separating fromproducts of said reaction a gas fraction, a fraction boiling in thegasoline boiling range and at least one heavierthan-gasoline fractionwhich includes tar.

12. The process of cracking a heavier-thangasoline hydrocarbon oil whichcomprises intimately contacting said oil at a temperature in the rangeof 125 to 300 C. with at least 50 percent by weight of a catalystconsisting of liquid hydrogen fluoride under a pressure suicient tomaintain liquid phase conditions and for a period of time suiliient toeiect cracking as the predominant reaction whereby a substantialproportion of the oil 1s converted into reaction products includinglow-boiling isoparain hydrocarbons, separating hydrogen fluoride from atleast a part of said reaction products and recov- 10 ering gasolineboiling range hydrocarbons as a principal product from that part of thereaction products.

l JOHN A. RIDGWAY, JR. PHILIP HILL.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS

